Ti Powder Research Articles

Fabrication and electromagnetic wave absorption modulation of high-performance (TaNbTiV)₂AlC MAX phase

Electromagnetic (EM) wave technology is widely used in both military and civilian applications, increasing interest in EM wave absorption materials for information security and environmental protection. This study examines the synthesis and EM wave absorption properties of M-site compositional complex MAX phase (TaNbTiV)2AlC. Using Ta, Nb, Ti, V, Al, and graphite powders, pure (TaNbTiV)2AlC was synthesized at 1400 °C. SEM and EDS confirmed homogeneous elemental distribution and morphology, while TEM and SAED analyses revealed the atomic structure. EM wave absorption was tested using (TaNbTiV)2AlC/paraffin wax composites with varying (TaNbTiV)2AlC content in the 2–18 GHz range. The main attenuation mechanisms identified were interfacial polarization, dielectric loss, and conductive loss. Optimal absorption was achieved at 30 vol% (TaNbTiV)2AlC, with a reflection loss of −43.83 dB and an effective absorption bandwidth of 3.49 GHz. The study demonstrates that the control of establishing a “near-conductive network” of fillers could be advantageous in achieving optimal electromagnetic wave absorption performance using fillers possessing high electrical conductivity, such as MAX phase materials.

The Use of TiH2 to Refine Y2Ti2O7 in a Nano Mo-ODS Alloy

Mo-ODS alloys have excellent mechanical properties, including an improved recrystallization temperature, greater strength due to dispersed oxides, and the ability to suppress grain growth at high temperatures. In ODS alloys, the dispersed Y2O3 and added Ti form Y-Ti-O complex oxides, producing finer particles than those in the initial Y2O3. The complex oxides increase high-temperature stability and improve the mechanical properties of the alloy. In particular, the use of TiH2 powder, which is more brittle than conventional Ti, can enable the distribution of finer oxides than is possible with conventional Ti powder during milling. Moreover, dehydrogenation leads to a more refined powder size in the reduction process. This study investigated the refinement of Y2Ti2O7 in a nano Mo-ODS alloy using TiH2. The alloy compositions were determined to be Mo-0.5Ti-0.5Y2O3 and Mo-1.0Ti-0.5Y2O3. The nano Mo-ODS alloys were fabricated using Ti and TiH2 to explore the effects of adding different forms of Ti. The sintered specimens were analyzed through X-ray diffraction for phase analysis, and the microstructure of the alloys was analyzed using scanning electron microscopy and transmission electron microscopy. Vickers hardness tests were conducted to determine the effect of the form of Ti added on the mechanical properties, and it was found that using TiH2 effectively improved the mechanical properties.

Synergistic densification mechanism of irregular Ti powder during CIP: 3D MPFEM simulation with real-shape particles

Achieving high green density is essential for ensuring the mechanical properties of powder metallurgy workpieces. However, the densification behavior of irregular ductile powders remains unclear due to oversimplification in current numerical simulations. To address this, a three-dimensional multi-particle finite element method model incorporating realistic powder morphology, size distribution, and stacking structure is constructed. It is found that a pivotal motion-deformation synergistic stage exists between the conventional particle rearrangement and elastic–plastic deformation stages. In this stage, plastic deformation is driven by the spheroidization of coarse powders, whereas the resulting vacancies in the stacking structure facilitate slight particle motion. Thereafter, plastic deformation is dominated by the flattening of fine particles, and the pore-filling capacity decreases due to the reduction in non-contact surface area. This synergistic and complementary interaction between the spheroidization of coarse powders and the flattening of fine powders enhances mechanical interlocking and promotes micropore closure. As a result, the micropores exhibit a tendency of downsizing and homogenization, substantially boosting the potential for achieving full densification during sintering. Based on these findings, a method for determining the optimal forming pressure is proposed, considering the manufacturing costs of powder compacts and the characteristics of the micropores in both green and sintered bodies.

Microstructure and tribological performance of novel Ni-based alloy cladding with excellent high temperature wear resistance and self-lubrication performance

This paper aims to study the laser cladding of Ni-based alloy coatings with excellent high temperature wear resistance and self-lubrication performance on the surface of parts such that meet complex metallurgical service conditions. The composite alloy powders were formed by adding 3 wt%–11 wt% WS2 and Ti powder to NiCrCoMoBSi alloy powder, and the novel Ni-based alloy samples with high temperature wear resistance and self-lubrication performance were cladded on the surface of Cr28Ni48W5 substrate by laser cladding. The results show that the addition of WS2 and Ti powder had a significant influence on the microstructure evolution and high temperature wear resistance and self-lubrication performance of the samples. The laser cladding coating with 7 wt% WS2 and Ti had the 3 % TiS self-lubricating phase and 19 % enhanced phase with the best microstructure matching relationship, which improved the high temperature wear resistance and self-lubrication performance of the sample. At 800 °C, compared with the Cr28Ni48W5 superalloy substrate, the friction coefficient of the laser cladding coating was 0.22 and the wear ratio was 1.70 × 10−5 mm3 N−1 m−1, which were reduced by 60 % and 54.67 % respectively. The mechanism of the enhanced wear resistance and self-lubrication performance was elaborated.

Protection behavior of Ti-SiO2 modified potassium silicate coating on K447a alloy at 1000 °C

Potassium silicate coatings cured by calcium hydrogen phosphate and modified by fillers of Ti and SiO2 powders were prepared on K447A alloy at 120 °C. The influences of Ti, SiO2 and both powders on the oxidation behavior of the coated specimens were investigated at 1000 °C for 100 h in static air by thermogravimetry, SEM, XRD and EPMA. The bare K447A alloy suffered severe oxidation at 1000 °C, and the TGO was found to be composited of an outer layer of mixtures of NiCr2O4, CoAl2O4 and rutile TiO2, and an inner α-Al2O3 layer. The potassium silicate coating without filler showed local damages where formation and rapid rupture of bubbles occurred and consequently the local substrate was oxidized. The SiO2 powder in the coatings is more capable of reducing O diffusion thru the coatings than the Ti powder, while the latter is more effective in getting rid of bubble rupture than the former. Thus, the coating modified by 10 wt% Ti and 20 wt% SiO2 showed the best protective performance.

Production of Low-Oxygen Ti Powder by Magnesiothermic Reduction of TiO2 in MgCl2–KCl–CeCl3 Molten Salt

Production of Low-Oxygen Ti Powder by Magnesiothermic Reduction of TiO2 in MgCl2–KCl–CeCl3 Molten Salt

Fabrication of customized open-cell titanium foams by direct foaming for biomedical applications

Titanium (Ti) foams offer a promising alternative for bone reconstruction and repair due to their high porosity and lower stiffness compared to solid metals, which improves in vivo osseointegration by reducing the stress shielding effect and allowing bone ingrowth. In this work, customized Ti foams were successfully fabricated for the first time at room temperature using a direct foaming method. Ti powder suspension with a water-soluble surfactant and environmentally friendly thickener was foamed by mechanical stirring. Then, 3D-printed moulds were utilized to achieve near-net shape foams, which were subsequently consolidated by sintering, thus avoiding the need for complex processing of molten Ti. The resulting Ti foams exhibited a cancellous-like open-cell structure, high porosity (> 80%), and a five times higher effective surface area than a 3D Ti mesh with a primitive cubic-based cell fabricated by additive manufacturing. In addition, the Ti foams exhibited similar mechanical properties to cancellous bone and facilitated the adhesion, proliferation, and maturation of human osteoblasts in vitro.

Effects of YH2 dopant on densification behavior, microstructure and mechanical properties of Ti–6Al–4V alloys

Ti6Al4V-xYH2 (x = 0, 0.1, 0.2, and 0.3 wt%) was produced in this research employing conventional powder metallurgy methods (cold pressing and sintering). The densification behavior, microstructure and mechanical properties of Ti6Al4V alloy caused by the addition of YH2 were systematically studied. The outcomes indicated that the Ti6Al4V containing 0.1 wt% YH2 has received a synergistic increase in ductility and strength (Ultimate tensile strength: 976.4 MPa; Elongation: 9.3 %), which is mainly attributable to the combined effect of grain refinement and purification of impurity oxygen. The study provides an economical approach for employing low-cost, high-oxygen HDH Ti powder to produce high-performance Ti material.

Co–Ni–Al–W γ/γ′ superalloy with Cr and Ti additions fabricated via laser fusion of elemental powders

A Co-based superalloy (Co-0.20Ni-0.11Al-0.07W-0.04Cr-0.03Ti, mole fraction) was synthesized by laser powder-bed fusion of a blend of elemental powders. The as-built alloy shows a γ-FCC matrix where the high-melting Ti and Cr powders are fully dissolved, but the refractory W particles are only partially melted. Full dissolution of the W particles is achieved after homogenization at 1150 °C, resulting in a homogeneous, single-phase γ microstructure. Upon aging at 900 °C, a two-phase γ/γ′ microstructure forms, with a high-volume fraction of sub-micron γ′ precipitates with cuboidal shape. Compared to a control quaternary alloy without Cr and Ti fabricated by the same method, the present alloy has increased γ′ fraction and microhardness after aging for 300 h, maintaining a strong γ′ strengthening effect without forming γ′-depleted zone at grain boundaries. Micrometer-size γ′-precipitates at grain boundaries also shift the transition between diffusional and dislocation creep to lower stress levels, by inhibiting diffusional creep and grain-boundary sliding. However, overall creep resistance is lowered, consistent with a reduction of lattice mismatch due to Cr additions and rafting of γ′ precipitates. Furthermore, Cr and Ti additions improve oxidation resistance at 900 °C, due to the formation of a continuous Cr-, Ti- and Al-rich oxide layer.

Timed Thermodynamic Process Model Applied to Submerged Arc Welding Modified by Aluminium-Assisted Metal Powder Alloying

An EERZ (effective equilibrium reaction zone) model was applied to the modified SAW (submerged arc welding) process to simulate the SAW process metallurgy in the gas-slag-metal reaction system. The SAW process was modified by adding Al as a de-oxidizer with alloying metal powders of Cr, Cu, and Ti. The static gas-slag-metal equilibrium model can accurately calculate the weld metal oxygen content (ppm O) for conventional SAW but not for the modified SAW process. The static equilibrium model overpredicts the reaction of Al. EERZ model runs were made for 2000–2500°C because this is the reported temperature range in the SAW arc cavity. The weld metal composition was adequately calculated, especially the weld metal ppm O, at the following effective equilibrium temperatures: 2400°C for Al-Cr additions, 2200°C for Al-Cr-Cu additions, and 2000°C for Al-Cr-Cu-Ti additions. Model results show that Ti metal powder can serve a de-oxidizer role in the presence of Al, resulting in Ti loss to the slag. Ti is also lost to the gas phase as TiF3(g) and TiF2(g) compared to little loss of Cr to the gas phase as Cr(g) and CrO to the slag phase.

Microstructure and Wear Resistance of In Situ Synthesized Ti(C, N) Ceramic-Reinforced Nickel-Based Coatings by Laser Cladding.

In recent years, laser cladding technology has been widely used in surface modification of titanium alloys. To improve the wear resistance of titanium alloys, ceramic-reinforced nickel-based composite coatings were prepared on a TC4 alloy substrateusing coaxial powder feeding laser cladding technology. Ti (C, N) ceramic was synthesized in situ by laser cladding by adding different contents (10%, 20%, 30%, and 40%) of TiN, pure Ti powder, graphite, and In625 powder. Thisestudy showed that small TiN particles were decomposed and directly formed the Ti (C, N) phase, while large TiN particles were not completely decomposed. The in situ synthetic TiCxN1-x phase was formed around the large TiN particles. With the increase in the proportion of powder addition, the wear volume of the coating shows a decreasing trend, and the wear resistance of the surface coating is improving. The friction coefficient of the sample with 40% TiN, pure Ti powder, and graphite powder is 0.829 times that of the substrate. The wear volume is 0.145 times that of the substrate. The reason for this is that with the increase in TiN, Ti, and graphite in the powder, there are more ceramic phases in the cladding layer, and the hard phases such as TiC, Ti(C, N) and Ti2Ni play the role in the structure of the "backbone", inhibit the damage caused by micro-cutting, and impede the movement of the tearing point of incision, so that the coating has a higher abrasion resistance.

Effect of Nb content on microstructural evolution, mechanical and tribological properties of in situ alloyed copper-modified titanium produced using laser powder bed fusion

Control of the columnar to equiaxed transition (CET) is a major challenge in additively manufactured β titanium alloys. In this work, the promotion of CET was successfully achieved through in-situ fabrication of Ti-5Cu (wt.%) alloys with additions of 5, 15, and 25 wt.% Nb using elemental Ti, Cu, and Nb powders by employing laser powder bed fusion (LPBF). The alloy containing 5 wt.% Nb consisted of α lamellae, Ti2Cu precipitates, and unmelted β-Nb inclusions, whereas the 25 wt.% Nb alloy consisted of equiaxed β grains, ω precipitates, and Ti2Cu precipitates at the grain boundaries. In terms of mechanical properties, despite the presence of Nb inclusions and liquation cracks in the 5 wt.% Nb alloy, it showed a yield strength of 1051 ± 40 MPa and an elongation of 5.2% ± 1.3%. Both the strength and ductility decreased with increasing Nb content, e.g., the 25 wt.% Nb alloy exhibited a yield strength of 808 ± 53 MPa and an elongation of 1.6% ± 0.2%. As the Nb content increased from 5 to 25 wt.%, the Young's modulus decreased from 110 to 65 GPa. The 25 wt.% Nb alloy showed a high ratio of hardness to Young's modulus (H/E) and yield pressure (H3/E2). However, due to its brittle nature, the material manifested high wear rates. These findings provide a basis for the future development of novel low-modulus isotropic β-titanium alloys using LPBF.

Complex-shaped titanium components fabricated via metal injection molding using hydride-dehydride titanium powder

Metal injection molding (MIM) is a net-shape manufacturing method that lessens the costs of production and increases the affordability of titanium goods. A range of CP-Ti specimens was prepared to confirm the primary manufacturing parameters for titanium metal injection molding utilizing affordable hydride-dehydride (HDH) powders. Mixture of powder and polyformaldehyde-based binder was injection molded, debonded, and then sintered. The optimum powder loading is 55 vol%. The ideal conditions of catalytic debinding were attained by placing the specimens in the catalytic debinding system at 120 °C temperature. Samples with minimal deformation and low impurity content were obtained when thermal debinding was carried out at a modest heating rate of 1.0 K/min and a holding time of 1.5 h. All the sintered samples have a similar microstructure, that is, lamellar α + β structure. The sample exhibits a strength of 739 MPa and an elongation of 6.1 % at the optimum sintering conditions (sintering at 1250 °C for 2 h). The samples prepared by MIM have excellent wear resistance. This process provided a straightforward and cost-effective means of producing complex-shaped titanium components from HDH Ti powder.

Tailoring Laser Powder Bed Fusion Process Parameters for Standard and Off-Size Ti6Al4V Metal Powders: A Machine Learning Approach Enhanced by Photodiode-Based Melt Pool Monitoring

An integral part of laser powder bed fusion (LPBF) quality control is identifying optimal process parameters tailored to each application, often achieved through time-consuming and costly experiments. Melt pool dynamics further complicate LPBF quality control due to their influence on product quality. Using machine learning and melt pool monitoring data collected with photodiode sensors, the goal of this research was to efficiently customize LPBF process parameters. A novel aspect of this study is the application of standard and off-size powder feedstocks. Ti6Al4V (Ti64) powder was used in three size ranges of 15–53 µm, 15–106 µm, and 45–106 µm to print the samples. This facilitated the development of a process parameters tailoring system capable of handling variations in powder size ranges. Ultimately, per each part, the associated set of light intensity statistical signatures along with the powder size range and the parts’ density, surface roughness, and hardness were used as inputs for three regressors of Feed-Forward Neural Network (FFN), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). The laser power, laser velocity, hatch distance, and energy density of the parts were predicted by the regressors. According to the results obtained on unseen samples, RF demonstrated the best performance in the prediction of process parameters.

Low-cost Ti-6Al-4V containing low content nano-carbon solid solution for achieving high strength and good ductility

With the rapid advancement of the aerospace industry, in addition to higher requirements for material properties, the cost-effective of its production have also attracted more attention. In this work, titanium matrix composite with high performance and low cost was designed using ball milling, spark plasma sintering and hot rolling process, i.e. hydrogenated dehydrogenated Ti and AlV powders as the precursor of Ti-6Al-4 V matrix, and a low content (0.15 wt%) reduced graphene oxide (rGO) with high-activity was selected to reinforce the matrix alloy. The as-rolled composite shows obvious texture orientation along the rolling direction without pores and microcracks. The incorporation of rGO led to the activation of the as-rolled composites along the {0001}[112¯0] type base slip. The as-rolled composite containing only 0.15 wt% rGO exhibits superior yield strength (1308.1 MPa) and ultimate tensile strength (1444.3 MPa), which are 11% and 9.3% higher than those of the matrix alloy, respectively, and the elongation remains at ∼5.6%. The strengthening mechanisms are mainly attributed to the solid solution strengthening effect of interstitial carbon in the matrix after the incorporation of rGO. This work highlights the development potential of low-cost and high-strength titanium matrix composites

Influence of Processing Parameters on Laser-Assisted Reactive Sintering of a Mixture of Ni and Ti Powders

Additive manufacturing (AM) plays a crucial role in the development of NiTi alloys, enabling the creation of complex and customized structures while optimizing properties for various biomedical and industrial applications. The aim of this paper was to investigate the influence of laser scanning speed on laser-assisted reactive sintering of a mixture of No and Ti powders. The samples were sintered at two different beam speeds, 4 and 5 4 mm/s and their morphological and microstructural characteristics were investigated. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) analyses revealed the presence of intermetallic compounds rich in Ni and Ti for both scanning speeds; however, the scanning speed of 5 mm/s produced a microstructure with greater porosity, leading to a sintered body with poorer consolidation. Thus, employing a slower beam scanning of 4 mm/s seems to be a better alternative in the laser-assisted reactive sintering of NiTi alloys.

Nanosecond pulsed laser irradiation of titanium in acetone: The effects of coating film structures on the hydrogen absorption properties

Pulsed laser irradiation was performed on titanium in acetone and then the hydrogen storage properties were investigated under a hydrogen atmosphere. TiOxCy films were formed by the irradiation of Ti powders with a fluence of 0.36 J cm−2. The irradiation increased the hydrogen absorption temperatures. Thus, the TiOxCy films showed a specific kind of hydrogen barrier effect. Irradiation with a fluence of 0.36 J cm−2 was performed to coat the Ti plate. Although the TiOxCy films formed on the surface, the amount of hydrogen absorption increased compared with the non-irradiated plate because of the change in surface chemical bonding states and high porosity of the films due to the irradiation. The phases generated by irradiation were controlled by the laser fluence. With a low fluence of 0.17 J cm−2, TiO2 films were formed instead of TiOxCy films, and these dense films showed better hydrogen barrier effects than the non-irradiated plate.

Pressure-less melt infiltration characteristics of Mg melt into Ti powder preforms with various pore structures: Toward the application to the binder jetting additive manufacturing

Binder jetting (BJT) additive manufacturing enables the fabrication of complex-shaped metallic parts but requires sintering as post-processing to obtain dense parts. The sintering inevitably causes the shrinkage from green body to dense products, resulting in low dimensional accuracy. In contrast, pressure-less melt infiltration (PMI) fills pores in the green body with a liquid metal driven by capillary pressure and fabricates a dense metal matrix composite without severe shrinkage. To consider the applicability of pressure-less melt infiltration to the post-processing of binder jetting additive manufacturing, it is required to clarify the relationship between pressure-less melt infiltration process conditions and the relative density of the composites. In this study, the liquid Mg/solid Ti system was selected because of good wettability and absence of Mg-Ti intermetallic, and the conditions of Ti powder preforms (corresponding to the green body) were focused on. Ti powder preforms with various powder sizes (2300, 410, 140, and 20 μm) and different shapes (irregular and spherical) were cold-pressed at 76, 102, 127, 153, and 178 MPa to fabricate preforms with various relative densities, pore sizes, and pore morphologies to response the similar characteristics in BJT preforms. Mg melt infiltrated into the preforms under constant conditions to fabricate Mg/Ti composites. The structures of the preforms and composites were characterized by sample size measurement, optical and scanning electron microscopy, and X-ray computed tomography. It was revealed that the relative density of the composite increased with decreasing Ti powder size and using spherical Ti powder, whereas the compact pressure exhibited a slight effect. Furthermore, defect volume increased with increasing infiltration height but decreased around the top surface of the sample. Minute observations around defects in the composites revealed that defects were formed at larger pores, and Mg melt was infiltrated into pores above the defects. These results indicated that infiltration velocity varied depending on the flow channel structure, and gas was trapped at larger pores (far from the outside of the sample) where infiltration velocity was low. Using smaller Ti powder decreased the variation in pore size in the preform, resulting in improving the relative density of the composites by suppressing the gas trapping. This study provides a new insight into the pressure-less melt infiltration process as a post-processing of binder jetting additive manufacturing.

A new concept of inoculation by isomorphic refractory powders and its mechanism for grain refinement

Isomorphic Inoculation (ISI) is a novel grain refinement technique during solidification by the addition of metallic powders to the melt rather than ceramics. The powders are designed to grow epitaxially rather than to nucleate new solid, increasing theoretically the ratio between solidified grains and inoculants to 1:1. This technique circumvents the energy barrier problems related to heterogenous nucleation in traditional grain refinement techniques. In this manuscript, we show through a combination of numerical and experimental techniques that this ratio could be reached. This is achieved through novel experimental techniques to replicate the effects of the melt on the powders. A new CaF molten salt experiment was used to, for the first time, show the recrystallization/grain growth of Ti powders at high temperature. In parallel, we calibrated a model on our experimental conditions and used it to calculate the dissolution rate of the powders in the melt. The combined effects of grain growth, preferential grain boundary dissolution (increasing the number of powders) and bulk dissolution (decreasing the number of powders) act together, bringing the number of particles present during solidification near that of the number of solidified grains found in the sample ingots. The per particle efficiency of this method is far in excess of traditional inoculation methods and has the potential for wide applications, especially in systems such as TiAl used here where the heterogeneous particles remaining in the as-cast material are undesirable.

Preparation of Ti3AlC2/Al2O3 composites based on the titanium concentrate: Gas-based reduction, acid leaching and sintering

Ti3AlC2/Al2O3 composites exhibit outstanding physical and chemical properties, but their widespread use is hindered by the expensive raw materials. This study introduces a novel production process for Ti3AlC2/Al2O3 composites. Initially, high grade Ti(C, O) powders with purity above 90 % are obtained through the reduction and carbonization of titanium concentrate in a CH4–H2 system. Subsequently, pure Ti3AlC2/Al2O3 composites are fabricated via sintering using the Ti(C, O)/Ti/Al system. Experimental findings reveal that prolonged reduction time and high temperatures in the CH4–H2 system lead to increased carbon deposition in the titanium concentrate reduction product, adversely impacting the purity of the sintered Ti3AlC2/Al2O3 composites. The optimal conditions for reducing titanium concentrate to Ti(C, O) in the CH4–H2 system involve a 1.5-h reduction period at 1200 °C. Excess Ti and Al powders are crucial in the preparation of Ti3AlC2/Al2O3 composites from the Ti(C, O)/Al/Ti material system. Surplus Ti powders reduce the TiC content in the final product, while excess Al powders act as deoxidizers, removing oxygen from Ti(C, O) and generating Al2O3 in situ. The optimal molar ratio for Ti(C, O), Al and Ti powders is determined to be 2:1.6:1.2. This research introduces a cost-effective approach for producing pure Ti3AlC2/Al2O3 composites.